metamorphic
Greenstone (likely nephrite jade or serpentinite)
Nephrite: interlocking actinolite–tremolite amphibole, Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂; possible serpentinite: Mg-rich phyllosilicates
AI-generated identification · may be incorrectDark green to gray-green, fine-grained and weakly waxy/dull luster; typically massive with no visible cleavage. Nephrite hardness is about 6–6.5 Mohs and very tough; serpentinite is softer, about 2.5–5.5.
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Physical properties
Dark green to gray-green, fine-grained and weakly waxy/dull luster; typically massive with no visible cleavage. Nephrite hardness is about 6–6.5 Mohs and very tough; serpentinite is softer, about 2.5–5.5.
Formation & geological history
Usually formed by metamorphism and metasomatism of ultramafic rocks in convergent-plate zones; likely Paleozoic–Mesozoic or younger depending on locality. The rounded surface indicates stream transport and weathering.
Uses & applications
Nephrite is used for carvings, cabochons, beads, and tools; serpentinite is used decoratively and occasionally as dimension stone. This unpolished specimen has modest commercial value.
Geological facts
The image alone cannot reliably distinguish nephrite from serpentinite or other greenstone. Nephrite feels unusually tough and resists scratching, while serpentinite commonly shows mottled, slick, or fibrous textures.
Field identification & locations
Common in ophiolite belts, alpine metamorphic zones, and alluvial gravels, including New Zealand, British Columbia, Wyoming, Russia, and China. Test on an inconspicuous area: steel may scratch serpentinite but generally will not scratch good nephrite; professional specific-gravity and microscopy tests are more reliable.
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